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Detector ready to receive beam of neutrinos.
Scientists have begun firing a beam of neutrinos through the Earth to a target 735 km (456 miles) away. This experiment will help the team understand how neutrinos can pass through tremendous amounts of matter, but barely interact. And if they're lucky, they'll catch the particles as they morph into different varieties: electron, muon and tau. One detector, at Fermilab, near Chicago, will sample the beam as it leaves the Main Injector. Another detector is stationed deep underground at the Soudan Mine in Northern Minnesota. Only muon neutrinos will be generated, so if the other varieties show up, scientists will know it happened in between the detectors.
Particle physicists from around the World are poised to unravel the secrets of the ethereal neutrino. Operational from this afternoon, March 4th, the Main Injector Neutrino Oscillation Search (MINOS) will produce a beam of neutrinos and fire them through the earth. By comparing neutrinos at the start with those that at the finish, some 735 km away, the scientists hope to understand many of their properties, including their most mysterious behaviour; how neutrinos can morph between three different types!
"This strange property of neutrinos was only recently discovered experimentally, because neutrinos interact with the their surroundings very rarely - in fact millions are passing through air, Earth and even people unnoticed at any given time. Even a specially built detector like the MINOS Far detector is only expected to see 1,500 neutrinos in a year - billions more will pass straight through!" says UK project spokesperson, Dr Geoff Pearce of the CCLRC Rutherford Appleton Laboratory.
The MINOS experiment will use a neutrino beam produced just outside Chicago, USA at Fermilab's Main Injector accelerator to probe the secrets of these elusive subatomic particles: where do they come from, what are their masses and how do they change from one kind to another? There are three types or 'flavours' of neutrino: electron, muon and tau, each with different properties. The neutrino beam will be projected straight through the Earth from Fermilab to the Soudan Mine in Northern Minnesota - a distance of 735 kilometres. No tunnel is needed because neutrinos interact so rarely with matter that they can pass straight through the Earth virtually unhindered. In a ceremony this afternoon, the Speaker of the US House of Representatives, the Honourable J. Dennis Hastert Jr. will activate the neutrino beam, sending the first particles on their journey to the detector in the Soudan mine.
Dr Alfons Weber, University of Oxford explains "This is an exciting time for us. The beam we now generate at Fermilab will contain only one type of neutrino - muon neutrinos. When it arrives at the Far Detector in the Soudan Mine fractions of a second later, some of the muon neutrinos will have changed into the other types - tau and electron neutrinos. We want to understand how they do this."
Two massive neutrino detectors have been built by MINOS, both of which are complete and ready for the beam. The 1000 ton 'near' detector will sample the beam as it leaves Fermilab and provide the control measurements. The 5,500 ton 'far' detector, half a mile underground in the Soudan Mine, will measure the neutrinos when they arrive, just 2.5 milliseconds later. The detectors have to be a long distance apart to allow the neutrinos, which travel at close to the speed of light, time to oscillate. "By comparing these two measurements we will be able to study how the neutrinos have oscillated and provide the world's most precise measurement of this effect with muon-type neutrinos" explains Dr Geoff Pearce.
Prof. Ian Halliday, CEO of the Particle physics and astronomy Research Council which funds UK work on this project, anticipated the revelations from the experiment's precision measurements.
"The mysteries of the elusive neutrino are about to be unveiled," Halliday said. "For the very first time we will be able to investigate the changing state of this bizarre particle to an unprecedented accuracy of a few percent in a controlled beam of neutrinos created in the laboratory. I'm extremely proud that UK scientists have played a key role in bringing this experiment to fruition and, in collaboration with their international colleagues, will be amongst the first in the world to study its unique characteristics."
"Physicists from around the world are trying to understand what these mysterious neutrinos are telling us," said Fermilab director Michael Witherell. "Today, we are embarking on a journey of exploration using the most powerful neutrino facility in the world. I am extremely proud of what the people of Fermilab have accomplished in completing the NuMI project. I would like to thank the American people and the federal government for making the necessary commitment to support great science."
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